c, ($\frac{1}{57}$ - $\frac{1}{5757}$ + $\frac{1}{23}$ )($\frac{1}{2}$ - $\frac{1}{3}$ - $\frac{1}{6}$ )

= ($\frac{1}{57}$ - $\frac{1}{5757}$ + $\frac{1}{23}$ )($\frac{3}{6}$ - $\frac{2}{6}$ - $\frac{1}{6}$)

= ($\frac{1}{57}$ - $\frac{1}{5757}$ + $\frac{1}{23}$ ) . 0

= 0

c, ($\frac{1}{99}$ + $\frac{12}{99}$ + $\frac{123}{9999}$ )(($\frac{1}{3}$ - $\frac{1}{5}$ - $\frac{2}{15}$ )

= ($\frac{1}{99}$ + $\frac{12}{99}$ + $\frac{123}{9999}$ ) ($\frac{3- 2 -1}{6}$ )

= $\frac{1}{99}$ + $\frac{12}{99}$ + $\frac{123}{9999}$ ).0

= 0

`c, ($\frac{13}{23}$ + $\frac{1313}{2323}$ - $\frac{131313}{232323}$ )($\frac{1}{3}$ + $\frac{1}{7}$ - $\frac{10}{21}$ )

= ( $\frac{13}{23}$+ $\frac{1313}{2323}$ - $\frac{131313}{232323}$ ) ($\frac{1}{3}$ + $\frac{1}{7}$ - $\frac{10}{21}$ )

=( $\frac{13}{23}$ + $\frac{1313}{2323}$ - $\frac{131313}{232323}$ )($\frac{1}{3}$ ( $\frac{7+3-20}{21}$ )

= $\frac{13}{23}$ . 0

= 0

 

`c, (1/57 - 1/5757 + 1/23)(1/2 - 1/3 - 1/6)`

`= (1/57 - 1/5757 + 1/23)(3/6 - 2/6 - 1/6)`

`= (1/57 - 1/5757 + 1/23). 0`

`= 0`

`c, (1/99 + 12/999 + 123/9999)(1/3 - 1/5 - 2/15)`

`= (1/99 + 12/999 + 123/9999)(5/15 - 3/15 - 2/15)`

`= (1/99 + 12/999 + 123/9999). 0`

`= 0`

`c, (13/23 + 1313/2323 - 131313/232323)(1/3 + 1/7 - 10/21)`

`= (13/23 + 1313/2323 - 131313/232323)(7/21 + 3/21 - 10/21)`

`= (13/23 + 1313/2323 - 131313/232323). 0`

`= 0`

`@Chyn`